Insulating strips have been utilized in building blocks in the past as disclosed in U.S. Pat. No. 3,204,381 to Perreton and in U.S. Pat. No. 3,546,833 to Perreton. HOwever, these prior art insulating strips were formed separately from the blocks and had to be manually inserted in the blocks prior to using the blocks to build a wall. Also, the dimensions and shape of the blocks were altered to adapt the blocks to receive the insulating strip.